H
Henry
Guest
RF Photo Flash Remote Control
At the suggestion of someone here I bought a set of the following parts
TLP434 Transmitter
RLP434 Receiver
HT12E Encoder
HT12D Decoder.
My project is to make my own remote RF flash trigger at a fraction of the
cost of the commercially made ones. I want multichannel ability so that if a
photographer friend an I are shooting in the same space that we are not
triggering each other's flash units. Something that happens with IR triggers
I am using now.
The diagram for using the above parts was so elegant and simple. After
building it, and fixing one wiring mistake, it WORK! P pressed the button on
the transmitter/encoder circuit on one breadboard and the LED lit up a
couple feet away on the receiver/decoder breadboard. However... I noticed
one problem. There was a slightly noticeable delay between pressing the
button and the LED lighting. I connected my camera hot shoe to act as the
button on the sending side, and my photo flash on the receiving side. Sure
enough, I could only sync as fast as 1/8 of a second. Not fast enough for
general photography. I need at least 1/60 second sync speed. Some new
cameras will sync as high as 1/250 second. But my goal is 1/125 if I can
achieve that.
I started checking different parts of the circuit. The encoding seems to
happen fast enough. The transmitting is also fast. The other circuit
receives the signal fast too. As far as I can tell, up to the point of
involving the decoder chip, everything happens almost instantaneous (to my
perception.) Most of the delay seems to be in the final decoding chip. Which
is sorta understandable as the chip has to watch the stream of signals from
the receiver and then recognize coded signal and match it up with the DIP
switches on its end.
I downloaded and read the HT12D spec sheet. My guess is that the problem is
that the HT12D&E are made for security uses (garage doors, electronic car
keys, etc.) So they use long 12 bit codes, and the Decoder chip waits for
(3) identical correct sequences in a row. So I figure all that checking
introduces the 1/10 second delay or so that is keeping this from working as
a fast remote photo flash trigger.
So, I need either a way to trick the decoder into working faster, on find a
different set of E/D pairs that work fast enough for me. I dont need the
long 12-bit/triple-check security. 4-bit/single (or double) check would be
fine for me. The encoding/decoding solutions need to be under about $10 each
or the project losses economic advantage. (I was thinking of offering to
build some of these for my other photography friends.)
Anyway, any ideas of getting the Decoder I have (HT12D) to work faster, or
an alternate solution that uses as much of the parts as possible that I
already have.
Sorry for the long post.
Henry
At the suggestion of someone here I bought a set of the following parts
TLP434 Transmitter
RLP434 Receiver
HT12E Encoder
HT12D Decoder.
My project is to make my own remote RF flash trigger at a fraction of the
cost of the commercially made ones. I want multichannel ability so that if a
photographer friend an I are shooting in the same space that we are not
triggering each other's flash units. Something that happens with IR triggers
I am using now.
The diagram for using the above parts was so elegant and simple. After
building it, and fixing one wiring mistake, it WORK! P pressed the button on
the transmitter/encoder circuit on one breadboard and the LED lit up a
couple feet away on the receiver/decoder breadboard. However... I noticed
one problem. There was a slightly noticeable delay between pressing the
button and the LED lighting. I connected my camera hot shoe to act as the
button on the sending side, and my photo flash on the receiving side. Sure
enough, I could only sync as fast as 1/8 of a second. Not fast enough for
general photography. I need at least 1/60 second sync speed. Some new
cameras will sync as high as 1/250 second. But my goal is 1/125 if I can
achieve that.
I started checking different parts of the circuit. The encoding seems to
happen fast enough. The transmitting is also fast. The other circuit
receives the signal fast too. As far as I can tell, up to the point of
involving the decoder chip, everything happens almost instantaneous (to my
perception.) Most of the delay seems to be in the final decoding chip. Which
is sorta understandable as the chip has to watch the stream of signals from
the receiver and then recognize coded signal and match it up with the DIP
switches on its end.
I downloaded and read the HT12D spec sheet. My guess is that the problem is
that the HT12D&E are made for security uses (garage doors, electronic car
keys, etc.) So they use long 12 bit codes, and the Decoder chip waits for
(3) identical correct sequences in a row. So I figure all that checking
introduces the 1/10 second delay or so that is keeping this from working as
a fast remote photo flash trigger.
So, I need either a way to trick the decoder into working faster, on find a
different set of E/D pairs that work fast enough for me. I dont need the
long 12-bit/triple-check security. 4-bit/single (or double) check would be
fine for me. The encoding/decoding solutions need to be under about $10 each
or the project losses economic advantage. (I was thinking of offering to
build some of these for my other photography friends.)
Anyway, any ideas of getting the Decoder I have (HT12D) to work faster, or
an alternate solution that uses as much of the parts as possible that I
already have.
Sorry for the long post.
Henry